42 lines
654 B
C
42 lines
654 B
C
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#include <stdio.h>
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#include <math.h>
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int pm(const long n);
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int main(void){
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long a,d,n;
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while(scanf("%ld %ld %ld",&a,&d,&n) == 3 && a+d+n){
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long now = a, count;
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if(!d && !pm(n)){
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printf("-1\n");
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continue;
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}
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if(pm(a) && n == 1){
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printf("%ld\n",a);
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continue;
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}
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for(count = 0; count < n;){
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if(pm(now)) count++;
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if(count >= n){
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printf("%ld\n",now);
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break;
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}
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now += d;
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}
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}
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return 0;
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}
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int pm(const long n){
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if(n == 1) return 0;
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else if(n == 2) return 1;
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long temp = n, sqtmp = sqrt(temp);
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int if_pn = 1;
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for(int k = 2; k <= sqtmp; k++){
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if(!(temp%k)){
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if_pn = 0;
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break;
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}
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}
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return if_pn;
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}
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