52 lines
1.3 KiB
C++
52 lines
1.3 KiB
C++
#include <iostream>
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#include <algorithm>
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#include <string>
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#include <set>
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#include <map>
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#include <utility>
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#include <queue>
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#include <stack>
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#include <list>
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#include <vector>
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#include <cstdio>
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#include <cstdlib>
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#include <cstring>
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#include <cmath>
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using namespace std;
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int main ()
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{
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string str;
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while ( cin >> str )
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{
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int N = str.size();
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int sum = 0, ask = 0;
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for ( int i = 1; i <= N; ++ i )
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{
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switch ( str[i-1] )
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{
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case 'X':
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sum += (10-i+1) * 10; break;
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case '?':
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ask = 10-i+1; break;
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default :
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sum += (10-i+1) * (str[i-1] - '0'); break;
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}
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}
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int pos = -1;
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for ( int i = 0; i <= 10; ++ i )
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{
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if ( ( sum + ask * i ) % 11 == 0 )
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{
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pos = i;
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break;
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}
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}
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if ( ask != 1 && pos == 10 ) pos = -1;
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if ( pos == 10 )
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cout << 'X' << endl;
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else
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cout << pos << endl;
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}
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return 0;
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}
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