15 lines
258 B
C
15 lines
258 B
C
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#include<stdio.h>
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int main(){
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int m;
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double ans[51];
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ans[1] = 3;
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ans[2] = 6;
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ans[3] = 6;
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for(int i=4;i<51;i++){
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ans[i] = ans[i-1] + 2*ans[i-2];
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}
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while(scanf("%d", &m)!=EOF){
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printf("%.0lf\n", ans[m]);
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}
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}
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